Conventionally, hybrid vehicles including an engine, two motors, and a controller for centrally controlling the engine and the motors have been known, as disclosed in JP 2010-188937 A. In the hybrid vehicles, two direct current (DC) power supplies are mounted in a state capable of respectively supplying electric power via power converters to the two motors, which are loads. The controller performs voltage control on one of the DC power supplies and power control on the other of the DC power supplies to individually control the power converters such that each motor is supplied with electric power necessary for an output requested of the motor.
It is further described in JP 2010-188937 A that, in the hybrid vehicle, the controller defines an upper limit value of a motor request power as the sum of limiting values associated with the DC power supplies when the engine is cranked by the motors, and defines the upper limit value of the motor request power as the sum of a target power value given to the DC power supply subjected to the power control and an output limit given to the DC power supply subjected to the voltage control when the engine is not cranked.
In the hybrid vehicle described in JP 2010-188937 A, there is a danger that electric power exceeding an output limit may be drawn from the DC power supply on a voltage control side at any time other than the time when the engine is cranked. This can happen in a case where responsivity of the power converter on a power control side is delayed relative to a change in power output request of the motor because such a delayed response results in a temporary shortage of power that should be delivered from the DC power supply on the power control side, and the shortage of power is compensated for by the DC power supply on the voltage control side while exceeding the output limit.
An advantage of the present invention is to appropriately prevent direct current (DC) power supplies from outputting power beyond output limitation in a power supply system equipped with a plurality of DC power supplies, and accordingly suppress progression of deterioration in the DC power supplies.